Unraveling the Photophysics of Liquid-Phase Exfoliated Two-Dimensional ReS2 Nanoflakes,The Journal of Physical Chemistry C

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Unraveling the Photophysics of Liquid-Phase Exfoliated Two-Dimensional ReS2 Nanoflakes
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2021-09-21 , DOI: 10.1021/acs.jpcc.1c05268
Pieter Schiettecatte _{1,

2} , Deepika Poonia ₃ , Ivo Tanghe _{1,

2} , Sourav Maiti ₃ , Michele Failla ₃ , Sachin Kinge ₄ , Zeger Hens _{1,

2} , Laurens D. A. Siebbeles ₃ , Pieter Geiregat _{1,

2}

Affiliation

Few-layered transition-metal dichalcogenides (TMDs) are increasingly popular materials for optoelectronics and catalysis. Among the various types of TMDs available today, rhenium chalcogenides (ReX₂) stand out due to their remarkable electronic structure, such as the occurrence of anisotropic excitons and potential direct band gap behavior throughout multilayered stacks. In this paper, we have analyzed the nature and dynamics of charge carriers in highly crystalline liquid-phase exfoliated ReS₂, using a unique combination of optical pump-THz probe and broad-band transient absorption spectroscopy. Two distinct time regimes are identified, both of which are dominated by unbound charge carriers despite the high exciton binding energy. In the first time regime, the unbound charge carriers cause an increase and a broadening of the exciton absorption band. In the second time regime, a peculiar narrowing of the excitonic absorption profile is observed, which we assign to the presence of built-in fields and/or charged defects. Our results pave the way to analyze spectrally complex transient absorption measurements on layered TMD materials and indicate the potential for ReS₂ to produce mobile free charge carriers, a feat relevant for photovoltaic applications.

中文翻译：

解开液相剥离二维 ReS2 纳米薄片的光物理学

少层过渡金属二硫属化物 (TMD) 是越来越受欢迎的光电和催化材料。在当今可用的各种类型的 TMD 中，铼硫族化物 (ReX ₂ ) 因其卓越的电子结构而脱颖而出，例如在整个多层堆叠中出现各向异性激子和潜在的直接带隙行为。在本文中，我们分析了高结晶液相剥离 ReS ₂中电荷载流子的性质和动力学，使用光泵浦太赫兹探头和宽带瞬态吸收光谱的独特组合。确定了两种不同的时间制度，尽管激子结合能很高，但两者都由未结合的电荷载流子主导。在第一时间范围内，未结合的电荷载流子引起激子吸收带的增加和加宽。在第二个时间范围内，观察到激子吸收曲线的特殊变窄，我们将其归因于内置场和/或带电缺陷的存在。我们的结果为分析分层 TMD 材料的光谱复杂瞬态吸收测量结果铺平了道路，并表明了 ReS ₂产生移动自由电荷载流子的潜力，这是一项与光伏应用相关的壮举。

更新日期：2021-09-30

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